Visual signal carrier indicator



Ressued 13, 1942 Earl I. Anderson, Bayside, `Long Island, N. Y.. assignor to Radio Corporation of America, a corporation of Delaware Original No. 2,194,518, dated March 2B, 1940,

Serial No. 201,591, April 12, 1938.

Application for reissue February 28, 1941, Serial No. 380,898

(ci. 25o-4o) 15 Claims.

My invention relates to visual signal indicators. and more particularly toga device for visually indicating the amplitude and resonance conditions of a received signal carrier.

One of the main objects of my invention is to provide a method of .indicating the strength of an incoming signal, and simultaneously indicating whether or not the receiver is properly tuned.

Another important object of the invention is to provide a visual signal indicator which indicates variatons in signal strength and improper tuningl by respectively different eifects; the device, additionally. informing the user of a receiver to which side of carrier resonance the re- `yceiver is tuned. and in which direction the receiver is to be adjusted in tuning in order to attain resonance. v

Another important object of this invention is to provide a visual current Y indicator of the cathode ray tube type. wherein the electron signal carrier voltage being applied between a.`

pair of deflection plates to convert the spot into a vertical line whose length is a function of the A' carrier strength: and the vertical line shifting to either side oi' a predetermined central position upon a shift in the carrier frequency, the shifting of the vertical line being caused by the application to another pair of deflection plates of a direct current voltage whose polarity and magnitude are a function of the direction and amount of carrier frequency shift.

Still other objects oi' my invention are to improvegenerally the efficiency and operation of visual signal indicators, and more particularly to provide an indicator arrangement which is not only reliable in operation. but is economically manufacty ed and assembled in a radio receiver.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims; the invention itself. however, as to both its organization and method oi operation will best be understood by` reference to the following description taken in effects desired: The receiving system isof the superheterodyne type, and only the I. F. ampliclaimed, by S. W. Seeley in application Serial stream is focused to cause a spot of light to apconnection with the drawing in which I have indicated diagrammati'cally a circuit organization whereby my invention may be carriedinto elect."

No. 45,413 illed Oct. 17, 1935, granted June 21. 1938 as U. S. Patent 2,121,103. The I. F. ampliiler i may have impressed upon its input terminals the I. F. energy produced in the usual first 'detector output circuit. It is to be understood' that the amplifier I may be preceded by any desired type of signal collector, the latter being foiv value of approximately 450 kc., the energyis.

amplified in the amplifier I, and then transmitted to the discriminator network through the magnetically coupled resonant circuits I and l. The resonant output circuit 2 includes the coil l and the shunt condenser l, the coil I vbeing magnetically coupled to the secondary coil l; the latter has the condenser 'l shuntedthereacross.

It will be understood that each of the resonant circuits 2 and l is flxedly` tuned to the operating Y I. F. valu. The high potential. point a of the.

primary circuit 2 is connected to the mid-point b of coil t through a direct current bloclng condenser C1.

The diode rectier 8 has its anode connected yto the point c of the secondary circuit 3, while the diode rectifier 9 has its anode connected to point d of thesecondary circuit. The cathodes l `of diodes I and 9 are connected through resistors Ri 'and Rz of equal magnitude. The junction D of these resistors is connected to the mid-point b through a path which includes the 1.1i'. illter elements lil arranged in series with the I. F.

cluding a visual indicator tube having circuit connections capable of producing th'e indication to the operating I. F. For carrier frequencies' Y' f choke coil Il. Appropriate I. Ii'. bypass oondensers I2 and il are respectively connected to ,ground from points -A and Bof the output load resistors of rectiilers l and 8. As explained in the aforesaid Seeley patent. the direct current voltage developed across resistors Ri and Rz is zero when the signal energy impressed on primary circuit 2 has a carrier frequency value equal which depart from this operating value there is developed a direct current voltage which is taken 4| shifts towards positions 42 or 42' Vdepending of! from point A, and whose polarity and magnitude depend upon the "direction and amount of shift respectively of the I. I". energy.

If the receiver is of the type employing automatic frequency control` (AFC), as shown in voltage may be tapped of! from'point D. It is not believed necessary to explain the uses for' work. Of course the audio voltage may be am-` plified in any desired audio network, and finally reproduced.

The I. F. energy at the primary circuit! is utilised, according to my invention, to denote It is slimclent t0 the aforesaid Seeley patent, AFC bias may be tapped oi! from point A, and AVC and audio.

visually variations inthe carrier amplitude.

Furthermore, the direct current voltage developed yat A is employed visually to indicate the direction and amount of I. F. carrier frequency departure. 'I'hese indications are produced on the uorescent screen of a cathode ray tube. The latter may be of the 913 type, if desired. However, for the purposes of this application the indicator tube is schematically represented. Those skilled in the`art are fully aware of the manner of construction tubes of this type. The tube comprises.

in general, an envelope 2li, and within the envelope is disposed an electron emitter 2 I a control grid 22 and successive focusing electrodes 2l and 2l for producing an electron beam.

The direct current voltage supply source may i comprise a potentiometer P; the emitter being tapped at a point 25 which is positive with respect to the g'rip tap point. The focusing anodes 23-24 may be connected to points on P which are successively more positive with respect to point 25. The four deflection plates 20-28' and 21-21' are arranged to act on the electron beam so as to produce the patternsto be described later. Plate 2l is connected to point a of primary circuit 2 through a direct current blocking vcondenser 2l; plates 2l' and 21' are connected to ground, as is the positive end oi' P. The plates 2l and 21' are connected to the point on P to-y which focusing anode Il is connected. A resistor 2l connects plate II to ground and plate 2l'. The y plate 21 is connected by the direct current voltage connection l0 to point A oi' the discriminator. In other words. I. F. carrier energy is applied to plates I-Il', whereas AFC bias (or, more gen-v erally, a frequency-responsive direct current voltage) is applied to plates 21-21.

'much positive as point d is negative.

Improper tuning, or frequency drift of the local oscillator, will cause a voltage to appear at point A. The polarity of the voltage depends upon whether the I. F. carrier frequency has shifted to the low or high side of the assigned frequency value, and the magnitudev of the voltage will depend upon the amount of frequency departure which in turn will determine the distance the vertical line moves laterally.

The following explanation is given of the mode of operation of the discriminator; this will make clear the relation between the I. F. energy frequency departure and the polarity and magnitude changes at point A. Assuming that the condenser C1 is so large that the voltage drop in it is negligible, it will be seen that the points a and b are at the same potential. Now. the phase of a with respect to ground potential is zero when the I. F. carrier has the assigned frequency value,

for at resonance there is ,no phase shift in the tank circuit. Thus,.the point b is at zero phase. The current in circuit 2 induces a voltage in circuit 3, and this is distributed equally about the mid-point b. At a given instant point c is as The voltages impressed on the two rectiiiers 8 and 9, .and the latter may be of the 6H6 type if desired, are. therefore, equal although opposite in phase. The rectified outputs depend only on the magnitudes, and, hence, the voltage drops across resistors R1 and R2 will be equal. Since the two rectiilers are connected in series opposition, 'the potential difference between points A and B will be zero. This balance occurs only when the frequencyis equal to the resonant frequency of the two loosely coupled circuits 2 and 3.

Suppose now that the I. F. carrier differs considerably from the resonant frequency. There will then be a phase shift of nearly 90 degrees in the circuit. The voltages induced in the two halves of the secondary coil 8 are still equal in magnitude, but they are opposite in phase with respect to point b. The voltage drop across circuit 2 is now added vectorlally to the induced voltages. Thus, the potential at one side of the secondary coil 6, say point c, will be the sum of the induced voltage b-c and the drop across circuit 2; on the other hand, the potential of the other end of coil- 6. that is point d, will be the difference between the drop in circuit 2 and the voltage in b-d. It follows that the input voltagevof one rectifier, the upper in the-assumed `case, is much greater than that in the other.

Therefore, the voltage drop will be greater across resistor Ri than that across Rz, and point A will be positive with point B. The point A will assume a negative polarity by\ assuming that the I. F. carrier departs yfrom their assigned frequency 1.' value in an opposite direction.

The numeral Il denotes the fluorescent screen of the indicator tube; the fluorescent coating on' the inner face of the viewing endv of the envelope on either side of the central point, into a vertical line when the carrier amplitude increases at I. F. resonance. However, when the I. F. carrier departs from the assigned frequency value, the line The screen end of envelope 20 may have calibrations placed on it to indicate more clearly the central position which corresponds to variations solely in carrier amplitude. Furthermore, the

1 off-resonance positions l2 and 42' can be' calibrated on the screen so that the user of the receiver is informed as to whether the receiver is detuned to the upper or lower side band of the signal carrier. It is, also, to be understood that the thicknessof the line 4I will depend on the relative positioning of the deflection plates and will readily be able to design the indicator tube electrodes so that the amplitude and/or resonanceindications are as pronounced as desired.

While I have indicated and described a systemv for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organization shown and described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is:

1. A method of operating a cathode ray tube of the type including a fluorescent screen, electron beam producing elements and at least two pairs of relatively perpendicular deflection electrodes; which includes impressing between a pair of deflection electrodes en electrical wave of a predetermined resonant frequency, producing a linear indication on the screen in response to variations in the said wave amplitude, and im pressing between a second pair of deflection electrodes a direct current voltage whose polarity is a function of the wave frequency departure from saidresonant frequency thereby to shift said linear indication on said screen. 4

2. In a method as defined in claim 1, maintaining said linear indication at a fixed centralposition on the screen during said wave amplitude variation, and rectifying said v vave to produce .i

said direct current voltage.

3. A method of indicating amplitude and frequency variations of the carrier of modulated carrier waves, and which method utilizes a cathode ray tube of the type employing a fluorescent screen, electron beam producing elements and at least two pairs of relatively perpendicular deflection elements; said method including impressing between a pair of deflection electrodes said waves thereby producing a line indication on the screen whose length is a function of the nitude depends upon the sense and amount of frequency departure of the said carrier from an assigned frequency value, and impressing said direct current voltage between a second pair of said deflection electrodes thereby to shift said line indication with respect to a predetermined point'on the screen representative of the amplitude variationindication.

4. A method of indicating amplitude and frequency variations of the carrier of modulated` carrier waves, which method includes the steps of `,translating carrier amplitude' variations into a visual linear indication whose length is a function of the carrier amplitude, deriving a direct current voltagey from the waves whose polarity and magnitude depends upon the sense and amount of frequency departure of the said carrier from an yassigned frequency value, and utilizing said direct curent voltage to shift said linear indication with respect to a predetermined point representative of the amplitude variation indication.

5. In a carrier wave indicator system. a tube of the type including means providimz` an electron beam. at least two pairs of relatively perpendicular deflection plates and a fluorescent screen, a carrier wave network tuned to a predetermined frequency, means coupling a pair o'f said deflection plates to said network thereby to impress carrier waves upon said pair of plates and produce a line indication on said screen carrier amplitude, deriving from said waves a 9' -direct current voltage whose polarity and maglili whose length is a function of the carrier amplitudevariation, means for deriving from the carrier waves in said network a direct current voltage whose polarity is a function of the departure of the carrier frequency from said predetermined frequency, and means for impressing said direct current voltage between a second pair of deflection plates thereby to shift said indication with respect to a point` on the screen corresponding to the amplitude variation indication.

6. In a system as defined in claim 5, said deriv ing' means including' a rectifier system having an input ,circuit resonant to said predetermined frequency and coupled tesaid network.

'7. In a system as defined in claim 5, means for maintaining said carrier amplitude line indication at the central portion of said screen, and said second pair` of deflection plates being positioned to shift said line indication either to the right or left depending upon vthe polarity of said direct current voltage.

`8. In a carrier wave indicator utilizing a tube of the type provided with an electron emitter, at least two pairs of relatively perpendicular `deflection plates and a fluorescent screen, the method which includes focusing an electron beam from said emitter upon said screen to provide a visual indication on the latter, deriving a direct current voltage from the Waves whose polarity and magnitude depend -upon the sense and amount of departure of the carrier frequency from an assigned frequency value, applying said voltage between one pair of said plates to shift the position of the'indication on, theV screen, and

applying wave energy between the second pair of plates thereby to vary said indication linearly.

i). A method ofindicating amplitude and fre' quency variations of the carrier of modulated carrier waves, which method includes the steps of translating carrier amplitude variations into a visual linear indication whose length is a func tion of the carrier amplitude,- and translating the frequency departure of the carrier from an assigne'd frequency value into shifts of said linear indication, with respect to a predetermined point representative of the `amplitude variation indication, which depend on the sense and amount of the frequency departure. i

10. A method of operating a cathode ray tube of the type including a fluorescent screen, electron beam producing elements and at least two pairs of relatively perpendicular deflection electrodes; which includes impressing between a pair of deflection electrodes an unrectifled electrical li. A method of indicating amplitude and fre` quency variations of theV carrier of modulated ycarrier waves, and which method utilizes a cathode ray tube of the type employing a fluorescent screen, electron beam producing elements and at least'I two pairs of relatively perpendicular deflection elements; said method including impressing between a pair of the deflection electrodes said waves in unrectifled form thereby producing an indication on the screen which is a function of the carrier amplitude, deriving from said waves a direct current voltage whose polarity and mag-l nitude depends upon the sense and amount of frequency departure of the said carrier from an assigned frequency value, and impressing said direct current voltage between a second pair of said deflection electrodes thereby to shift said` indication with respect to a predetermined point on the screen representative of the amplitude variation indication.

12. A method of indicatingl amplitude and frequency variations of the carrier of modulated carrier waves, which method includes the steps of translating carrier amplitude variations into a variable visual indication without rectification of the'carrier waves, deriving a direct current voltage from the waves whose polarity and magnitude depends upon the senseand amount of frequency departure of the said `carrier from an assigned frequency value, and utilizing said direct current voltage to shift said indication with respect to a predetermined point.

13. In a carrier wave indicator utilizing a tube of the type provided with an electron emitter, at least two pairs of relatively perpendicular defiection plates and a uorescent screen, the

" method which includes focusing an electron beam from said emitter upon said screen to provide a visual indication on the latter. deriving a direct current voltage from the waves whose polarity and magnitude depend upon the sense and amount of departure o f the carrier`frequency from an assigned frequency valuel applying said voltage between one pair of said plates to shift the position of the indication onthe screent-,and controlling said beam with unrectied carrier wavesy in response to solely carrier amplitude variation to. vary said indication.

14. A method of indicating amplitude and frequency variations of the carrier of modulated carrier waves, which method includes the steps of utilizing unrectiiied carrier waves to translate carrier amplitude variations into a visual indication having a characteristic which is a function of the carrier amplitude. and utilizing rectied carrier waves for translating the frequency departure of the carrier from an assigned frequency Avalue into shifts of said indication, with respect to a predetermined point representative of the amplitude variation indication, which depend on the sense yand amount of the frequency departure.

l5. A method of indicating amplitude and frequency changes ofthe center frequency of modulated zcarrier waves, which includes producing an electron beam, causing the beam to provide a visual indication, controlling with unrectified carrier waves a characteristic ofthe indication in response to said amplitude changes, and controlling with rectified carrier waves said beam in response to said frequency changes to displace said indication.

EARL I. ANDERSON. 

